Electricity: electrical systems and devices – Electrolytic systems or devices – Liquid electrolytic capacitor
Reexamination Certificate
1998-06-24
2001-04-03
Kincaid, Kristine (Department: 2831)
Electricity: electrical systems and devices
Electrolytic systems or devices
Liquid electrolytic capacitor
C361S516000, C361S508000, C361S504000, C361S502000, C607S005000
Reexamination Certificate
active
06212063
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to implantable medical devices such as defibrillators and AIDs, and their various components, including flat electrolytic capacitors for same, and corresponding methods of making and using same.
BACKGROUND OF THE INVENTION
Implantable medical devices for therapeutic stimulation of the heart are well known in the art. In U.S. Pat. No. 4,253,466 issued to Hartlaub et al., for example, a programmable demand pacemaker is disclosed. The demand pacemaker delivers electrical energy, typically ranging in magnitude between about 5 and about 25 micro Joules, to the heart to initiate the depolarization of cardiac tissue. This stimulating regime is used to treat heart block by providing electrical stimulation in the absence of naturally occurring spontaneous cardiac depolarizations.
Another form of implantable medical device for therapeutic stimulation of the heart is an automatic implantable defibrillator (AID), such as those described in U.S. Pat. No. Re. 27,757 to Mirowski et al. and U.S. Pat. No. 4,030,509 to Heilman et al. Those AID devices deliver energy (about 40 Joules) to the heart to interrupt ventricular fibrillation of the heart. In operation, an AID device detects the ventricular fibrillation and delivers a nonsynchronous high-voltage pulse to the heart through widely spaced electrodes located outside of the heart, thus mimicking transthoracic defibrillation. The technique of Heilman et al. requires both a limited thoracotomy to implant an electrode near the apex of the heart and a pervenous electrode system located in the superior vena cava of the heart.
Another example of a prior art implantable cardioverter includes the pacemaker/cardioverter/defibrillator (PCD) disclosed in U.S. Pat. No. 4,375,817 to Engle et al. This device detects the onset of tachyarrhythmia and includes means to monitor or detect the progression of the tachyarrhythmia so that progressively greater energy levels may be applied to the heart to interrupt a ventricular tachycardia or fibrillation.
Another device is an external synchronized cardioverter, such as that described in “Clinical Application of Cardioversion” in Cardiovascular Clinics, 1970, Vol. 2, pp. 239-260 by Douglas P. Zipes. This type of external device provides cardioversion shocks synchronized with ventricular depolarization to ensure that the cardioverting energy is not delivered during the vulnerable T-wave portion of the cardiac cycle.
Another example of a prior art implantable cardioverter includes the device disclosed in U.S. Pat. No. 4,384,585 to Douglas P. Zipes. This device includes circuitry to detect the intrinsic depolarizations of cardiac tissue and pulse generator circuitry to deliver moderate energy level stimuli (in the range of about 0.1 to about 10 Joules) to the heart synchronously with the detected cardiac activity.
The functional objective of such a stimulating regimen is to depolarize areas of the myocardium involved in the genesis and maintenance of re-entrant or automatic tachyarrhythmias at lower energy levels with greater safety than was possible with nonsynchronous cardioversion. Nonsynchronous cardioversion always incurs the risk of precipitating ventricular fibrillation and sudden death. Synchronous cardioversion delivers the shock at a time when the bulk of cardiac tissue is already depolarized and is in a refractory state. Other examples of automatic implantable synchronous cardioverters include those of Charms in U.S. Pat. No. 3,738,370.
It is expected that the increased safety deriving from use of lower energy levels and their attendant reduced trauma to the myocardium, as well as the smaller size of implantable medical devices, will expand indications for use beyond the existing patient base of automatic implantable defibrillators. Since many episodes of ventricular fibrillation are preceded by ventricular (and in some cases, supraventricular) tachycardias, prompt termination of the tachycardia may prevent ventricular fibrillation.
Consequently, current devices for the treatment of tachyarrhythmias include the possibility of programming staged therapies of antitachycardia pacing regimens, along with cardioversion energy and defibrillation energy shock regimens in order to terminate the arrhythmia with the most energy-efficient and least traumatic therapies, when possible. In addition, some current implantable tachycardia devices are capable of delivering single or dual chamber bradycardia pacing therapies, as of which are described, for example, in U.S. Pat. No. 4,800,833 to Winstrom, U.S. Pat. No. 4,830,006 to Haluska et al., and U.S. patent application Ser. No. 07/612,758 to Keimel for “Apparatus for Delivering Single and Multiple Cardioversion and Defibrillation Pulses” filed Nov. 14, 1990, and incorporated herein by reference in its entirety. Furthermore, and as described in the foregoing '833 and '006 patents and the '758 application, considerable study has been undertaken to devise the most efficient electrode systems and shock therapies.
Initially, implantable cardioverters and defibrillators were envisioned as operating with a single pair of electrodes applied on or in the heart. Examples of such systems are disclosed in the aforementioned '757 and '509 patents, wherein shocks are delivered between an electrode is placed in or on the right ventricle and a second electrode placed outside the right ventricle. Studies have indicated that two electrode defibrillation systems often require undesirably high energy levels to effect defibrillation.
In an effort to reduce the amount of energy required to effect defibrillation, numerous suggestions have been made with regard to multiple electrode systems. Some of those suggestions are set forth in U.S. Pat. No. 4,291,699 to Geddes et al., U.S. Pat. No. 4,708,145 to Tacker et al., U.S. Pat. No. 4,727,877 to Kallock, and U.S. Pat. No. 4,932,407 issued to Williams where sequential pulse multiple electrode systems are described. Sequential pulse systems operate based on the assumption that sequential defibrillation pulses delivered between differing electrode pairs have an additive effect such that the overall energy requirements to achieve defibrillation are less than the energy levels required to accomplish defibrillation using a single pair of electrodes.
An alternative approach to multiple electrode sequential pulse defibrillation is disclosed in U.S. Pat. No. 4,641,656 to Smits and also in the above-cited '407 patent. This defibrillation method may conveniently be referred to as a multiple electrode simultaneous pulse defibrillation method, and involves the simultaneous delivery of defibrillation pulses between two different pairs of electrodes. For example, one electrode pair may include a right ventricular electrode and a coronary sinus electrode, and a second electrode pair may include a right ventricular electrode and a subcutaneous patch electrode, with the right ventricular electrode serving as a common electrode to both electrode pairs. An alternative multiple electrode, single path, biphasic pulse system is disclosed in U.S. Pat. No. 4,953,551 to Mehra et al., which employs right ventricular, superior vena cava and subcutaneous patch electrodes.
In the above-cited prior art simultaneous pulse multiple electrode systems, delivery of simultaneous defibrillation pulses is accomplished by simply coupling two electrodes together. For example, in the above-cited '551 patent, the superior vena cava and subcutaneous patch electrodes are electrically coupled together and a pulse is delivered between those two electrodes and the right ventricular electrode. Similarly, in the above-cited '407 patent, the subcutaneous patch and coronary sinus electrodes are electrically coupled together, and a pulse is delivered between these two electrodes and a right ventricular electrode. See also U.S. Pat. Nos. 5,411,539; 5,620,477; 5,6589,321; 5,545,189 and 5,578,062, where active can electrodes are discussed.
The aforementioned '758 application discloses a pulse generator for use
Breyen Mark D.
Bullock Norma K.
Di Domenico Edward
Hobot Christopher M.
Johnson William L.
Kincaid Kristine
Medtronic Inc.
Patton Harold R.
Thomas Eric V.
Woods Thomas F.
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